Method of manufacturing an electric coil



Fgb. 24, 1959 E. G. HOFER ET AL 2,875,420

METHOD OF MANUFACTURING AN ELECTRIC COIL Filed March 27, 1956 EUGENE G. HOFER PAUL J. KOPPE SIEGFRIED R. MISCHNICK.

INVENTORS.

THEIR ATTORNEY.

United States Patent C METHOD OF MANUFACTURING AN ELECTRIC COIL.

Eugene G. Hofer, Chicago, Paul J. Koppe, Niles, and Siegfried R. Mischnick, Chicago, Ill., assignors to Zenith Radio Corporation, a corporation of Delaware Application March 27, 1956, Serial No. 574,208

1 Claim. or. 336-192) This invention relates generally to a multi-tapv electric coil and more specifically relates to a method of 'construction of transformer coils, or the like, having a plurality of taps and to the manner of making connections between the taps and lead wires.

The coils of modern power transformers as used in various installations, as for example in television sets, may have a considerable number of taps. The purpose of the taps, of course, is to provide a number of different voltages for difierent specific purposes from a common winding of a common core.

In the past such transformers have been wound with several layers of parallel turns of wire insulated by a coating of enamel, or other insulating material. The coils may be wound on any suitable core in successive layers which are separated from each other by inserts or layers of separating material as, for example, paper or similar insulating material. For protection, the outermost layer of wires is usually wrapped in a circumferential direction by a strip of material of suitable strength and toughness such as varnished cambric or the like.

Quite commonly the transformer may consist of many turns of fine gauge wire such that much difliculty is usually encountered in connecting the fine gauge taps to much larger wire leads to be connected in the proper circuit. Therefore, great care is given to insure proper connection between the taps and leads and to properly anchor the lead wires to the transformer to prevent breakage of the fine wire taps during handling of the transformer.

Therefore it is seen that the construction of transformer coils in the past has involved many steps of time consuming operations which greatly increases the cost of the finished product.

Therefore, one of the principal objects of this invention is to provide a new and improved method and means whereby the fine gauged wire of the coil taps may be connected to lead wires with a minimum of labor and waste so as to maintain the cost thereof at a minimum.

Another object of this invention is to provide a new and improved and efficient method and means whereby the lead wires may be effectively anchored with a minimum of labor to prevent the taps from being subjected to tensional stresses and strains when in service and to maintain the cost thereof at a minimum.

A further object of the invention is to provide a new and improved method and means for applying the final protective covering on the outer layer of the coil winding which can be accomplished in a minimum of time and with a minimum of steps and adaptable for mass production to maintain the cost thereof at a minimum.

In accordance with the present invention, there is provided a new and improved method of manufacturing an electric coil assembly having the terminal portions of a plurality of lead wires individually connected to the end portions of a corresponding plurality of tap wires projecting from concentric convolutions of the coil with the junctions of the lead and tap wires covered by a strip of insulating material bondable to itself. More particularly, the method contemplates the steps ofrinitial- 1y securing the lead wires directly to the, strip of insulating material and then Wrapping the strip entirely around. the. circumference of the coil, leaving the secured lead wires exposed and also leaving a continuing portion of the strip projecting away from the coil. Thereafter terminal portions of the lead wires are individually joined electrically to end portions of the tap wires. The continuing portion of the strip is then wrapped around the" coil, over and beyond the joined lead and tap wires and a region of the continuing portion of the strip beyond the joined lead and tap wires is bonded directly to the underlying layer of the strip.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claim. The organization and manner of operation of the invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in the several figures of which like reference numerals identify like elements, and in which:

Figure l is a perspective view of the transformer illustrating the principle of the invention; and

Figure 2 is a perspective view of the transformer illustrating a slightly modified version of the invention.

With reference to Figure 1 of the drawings, transformer coil 10 is wound on an insulating coilform 11 in a conventional manner with a layer of insulating material between the convolutions of the coil. The taps 12 are brought out in conventional manner to extend along opposite edges of the coil. The outermost layer of wires are protected by a strip of insulating material 13 having lead wires 14 stapled or otherwise secured thereto which is then wound tightly about the circumference of coil 10 and having a free end 15 remaining. The insulating strip may be of any material of suitable strength and toughness such as cellulose acetate, gummed cambric or any suitable adhesive wrappings. Tap leads 12 are soldered or otherwise electrically connected to larger gauged lead-in wires '14 and the connections thereof are then covered by a protective insulating strip 16 placed thereover which may be of any suitable adhesive paper or the like which is firmly pressed into engagement therewith so that it adheres firmly to both the wrapping 13 and leads 12 and 14. The adhesive strip is held securely in place by overlapping the other end 15 0f the insulating tap 13 which is then cemented or otherwise secured to the periphery of coil 10. Preferably, it has been found desirable to utilize an insulating strip, such as 13, of cellulose acetate Whose free end 15 is cemented to itself by proper application of acetone or the like.

If tape 13 is rendered adhesive on the innermost side thereof, the necessity of cementing the loose end 15 to the periphery of the coil is eliminated but .will be adhesively united with the periphery of the coil.

With reference to Figure 2 of the drawings, an L- shaped protective insulating member 17 may be utilized instead of an adhesive strip 16 which is positioned over taps 12 and lead-ins 14 and held securely in place by loose end 15 overlapping tightly thereover.

Thus the present invention provides a new and improved method for constructing and making connections of a plurality of taps of a transformer to a plurality of lead-in wires which may be accomplished with a minimum number of steps in a minimum of time while at the same time providing the necessary rigidity to prevent asreaao breakage of the small gauged taps of the transformer during use thereof, thus making it possible to construct such a transformer with a minimum of cost.

While particular embodiments of the invention have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made Without departing from the invention in its broader aspects, and, therefore, the aim in the appended claim is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

We claim:

The methodof manufacturing an electric coil assembly having the terminal portions of a plurality of lead wires individually connected to the end portions of a corresponding plurality of tap wires projecting from a coil of concentric convolutions of an electrical conductor with the junctions of said lead and tap wires covered by a strip of insulating material bondable to itself, said method comprising the steps of: initially securing said lead wires i directly to said strip; subsequently wrapping said strip entirely around the circumference of said coil, leaving the secured lead wires exposed and also leaving a continuing portion of said strip projecting away from said coil; electrically joining the terminal portions of said lead wires individually to the end portions of said tap wires; wrapping said continuing portion of said strip around said coil over and beyond the joined lead and tap wires; and bonding a region of Said continuing portion beyond the joined lead and tap wires directly to the underlying layer of said strip.

References Cited in the file of this patent UNITED STATES PATENTS 2,072,635 Helgason et a1. Mar. 2, 1937 2,184,272 Driftrneyer Dec. 26, 1939 2 ,275,967 Keillor et al. Mar. 10, 1942 2,633,481 Meeks Mar. 31, 1953 

